1. Field of the Invention
The present invention relates to a data processing apparatus, a data processing method, an ink jet printing apparatus, and an ink jet printing method that are related to a printing method using a dot arrangement pattern. In particular, the present invention relates to a data processing apparatus, a data processing method, an ink jet printing apparatus, and an ink jet printing method for performing, when a plurality of types of inks are used for a printing, the printing so that quantized data (n value) that is n-valued (n=3) is developed, with regards to different ink, to provide a dot arrangement pattern having L (width)×M (length).
2. Description of the Related Art
With regards to an ink jet printing apparatus, efforts have been made recently to print an image having a higher quality by providing a printing droplet (ink droplet) having a smaller size. On the other hand, suggestions have been made to realize a high-speed processing of image data.
Japanese Patent Application Laid-open No. 9-46522 suggests a conversion processing method for converting inputted image data such that each of a plurality of printing colors is converted independently. The term “conversion processing” in this case intends to mean a quantized processing for a relatively low resolution and multiple values by a host apparatus. Image data subjected to this conversion processing is transferred to an ink jet printing apparatus. The printing apparatus converts the received image data that has a low resolution and that is highly quantized into a predetermined dot arrangement pattern to perform a printing based on this dot arrangement pattern (so-called dot matrix printing).
The printing method using a dot arrangement pattern as described above has involved some suggestions. For example, a plurality of dot arrangement patterns having different dot arrangements are previously prepared with regards to input image data having the same signal level (same tone level) so that a dot arrangement pattern selected from the plurality of dot arrangement patterns is allocated to the image data. In this case, with regards to a method for selecting a dot arrangement pattern to be allocated, some methods have been suggested, including a method for selecting a dot arrangement pattern depending on the position of the pixel data, a method for selecting a dot arrangement pattern based on a random number value consisting of a predetermined bit number, and a method for sequentially switching a to-be-used dot arrangement pattern depending on the existence or nonexistence of image data in a pixel array.
However, the printing of dot matrix as described above has a risk of causing a defect as described below.
In the case where a serial scan type ink jet printing apparatus is used to print an image for example, when image data having the same tone level continues, a risk causing periodic density fluctuation on a printing image in the main scanning direction may be caused while a carriage including a printing head is moved. This is presumably caused, for example, by an accuracy with which the printing head is attached to the carriage, the ink impact accuracy, and an error of the carriage feeding accuracy in the printing apparatus body.
In the case of a printing head in which a plurality of printing element arrays (nozzle arrays) are arranged in parallel in the main scanning direction (printing head having a so-called lateral arrangement) and in which one printing color (ink color) is associated with a plurality of printing element arrays, there may be a case in which the distance between printing element arrays may be different depending on each associated printing color. In this case, due to the carriage feeding accuracy in the main scanning direction for example, the level of displacement of the ink impact positions is different among printed colors, causing a risk in which periodic density fluctuation in the main scanning direction may be more remarkable. The density fluctuation described above has a close relation with a dot coverage rate per a pixel (unit pixel) (so-called area factor). Specifically, in the case where dots having different colors are arranged in a single pixel, when periodic displacement of ink impact position is caused in the sub scanning direction crossing the main scanning direction, the level of interference among dots for different colors is changed. Thus, some regions include a relatively large change of a so-called area factor while other regions include a relatively small change of a so-called area factor. This causes a periodic color displacement in the main scanning direction, causing density fluctuation to human eyes.